By comparing existing moveable pile drivers, the advantage of the present invention is that the pile driver can drive all the piles within a pile group and yet selectively raked them to various degrees in any two axes. Whereas the existing prior arts using the push pull method used for driving sheet and tube piles in an alignment has drawbacks in that cannot raked piles in one or even two axes nor drive adjacent piles perpendicular to the alignment.
This present invention consists of a cluster of modular pile driver units with each overall cross-sectional dimension less than three times the pile diameter so that the driven pile's centre to centre spacing is at a minimum of three times the pile's diameter to reduce the pile cap size.
Further, unlike the common bulky heavy counter-reaction loads used in the prior arts like the hydraulic static pile driver, the present invention is very small and compact, therefore suited to drive piles in confined urban areas like in the road median with minimum traffic diversion, etc.
US20070144360A1 specifies a multiple press with adjustable spacing in a common horizontal rail; therefore it cannot drive raked piles in one or even two axes nor drive adjacent piles perpendicular to the alignment.
JP6-193065 teaches the common push pull pile driver in an alignment that comprises of at three pulling clamps held together in a rigid base frame to support and push the front pile; therefore it cannot drive raked piles in one or even two axes nor drive adjacent piles perpendicular to the alignment
JP2002-129566 teaches the use of a single pull resistant pile assisting a push pile driver in addition to the push down force of the excavator. This method without more than two pull clamps to provide resistance against driving reaction force is limited by the maximum friction of the single pile which is insufficient if it encounters an obstruction or hard driving.
Korean patent 10-0792130 shows a pile being driven downwards with four resisting tension rods anchored into a common heavy slab. The four hold down tension rods is fixed and cannot be further driven. This prior art can only drive one central pile into the ground instead advancing a group of piles in a sequence into the ground as in push and pull method which theoretically gains increased combined frictional resistance as the piles penetrates into the ground.
JP2004-1562219A teaches the use of four driven stakes that is used as a reaction piles to provide resistance against the driving of a centrally located pile. These four exterior stakes may be screw piles which is usually large but shallowly embedded into the ground. There is no intention to use these shallow screw reaction piles as permanent piles as the centre permanent tabular piles must be driven deeper into more competent strata below.
JP63-23218 and JP02-030809 teaches pile driving using auxiliary anchor set in the position to the frame. As in the prior arts mentioned above, this method can only drive the central pile and cannot drive by advancing all the piles progressively into the ground like the push and pull method.
Korean patent 10-2008-0004222 teaches of an adjustable top and bottom pile guide that can slide along a frame in plane therefore raking the pile. However as compared to the present invention, it can only rake in one axis.
Russian patent 2273694C1 teaches of a method of stabbing the pile using four funnel piling guides positioned in subsea piling. The funnel piling guides are fixed in-line with the exterior axis of the legs of the jacket structure, but it did not teach that the four funnel piling guides can be further variably adjusted by rotating about the x-axis and y-axis as compared to the present invention.
PCT/MY2011/000054 teaches a pile swivelling clamp but faces the problem of the heavy clamps dropping downwards in relation to the centre of the clamp housing. The present invention overcomes this problem by providing a centralising plate that holds all the clamps centrally in relation to the top and bottom clamp housing by vertically compressed springs.
Therefore, in addition to overcoming the problems faced by the fore-mentioned prior arts, the present invention has the following advantageous features; compact pile driver units using powerful clamping system contained inside a compact body with peripheral lugs to be closely inter-connected by steel pins in dowel action to the modular base frame. In addition, the base of the frame can also be attached with a movable sliding base or powered track wheels to make the pile driver self-mobile.
To reduce the pile cap size, it is necessary that the group piles be driven at an optimum pile's centre to centre spacing of 3d (three times the pile's diameter or cross-section dimension). This is only possible if the pile driver unit has dimensions smaller than 3d so that the multiple pile driver units can be placed next to each other.
Conventionally, huge side pile clamps must be required to deliver a side clamping force of exceeding 5-7 times the driving force to avoid the pile/clamp interface slippage. With this present invention, the pile driver units does not require huge side pile clamps as in the prior arts because it can convert the vertical driving force directly through the sliding mechanisms of the wedges into a side horizontal clamping force.
Furthermore, it is the salient feature of this invention that through the use of a pile driver base adaptor, the pile driver units can be connected to the base frame raked from 1V:1H to a true vertical in the z-axis and be rotated to any angle in the x-y plane. This is particularly important for foundations that require lateral stability like piers and tall cantilever structures.
The modular frame based can also be configured to contain pile driver units arranged in a matrix of 1×3, 2×2, 3×2, 3×4, etc groups. The attachment of the modular base frame is held together by means of fasteners sufficient to cope with the bending of the base frame during pile driving.
The use of a circular or tabular housing to provide the transfer of jacking loads on to the clamping system and interconnected by a base frame is advantageous as is it is compact and sturdy system.